Because Drosophila melanogaster has well developed capacities to tolerate the toxic effects of high levels of ethanol and to use low levels of ethanol for food, it provides a model system for studying biochemical and genetic changes that are associated with repeated exposures to environmental ethanol. Since more than 90% of the dietary ethanol is degraded by the alcohol dehydrogenase (ADH) pathway in D. melanogaster it is important to learn how the pathway is regulated and what its components are. We will investigate the molecular basis of the induction of ADH by ethanol, a process that may be important to the adaptation of the animal to environmental ethanol. Whether ADH or an aldehyde dehydrogenase catalyzes the acetaldehyde-to acetate step of the ADH pathway of ethanol degradation will be examined and the properties of ADH determined to ascertain whether it performs a non-alcohol function that is important to lipid synthesis. Since the enzymes of the glycerol- 3-phosphate cycle, sn-glycerol-3-phosphate dehydrogenase and sn- glycerol-3-phosphate oxidase, appear to be important to ethanol tolerance in D- melanogaster, experiments will be performed to define these roles and to determine how these enzymes interact ADH in lipogenesis. We will also investigate whether ethanol- stimulated changes in lipid composition are important to the alcohol tolerance. Most D. Melanogaster populations are polymorphic for different alleloenzymes of ADH. We will assess whether different ADH alleloenzymes differentially influence metabolic flux through the ADH pathway and consequently confer different fitnesses to D. Melanogaster in an ethanol environment. We will also quantify the contributions of alternate pathways to ethanol degradation. P-element transformed lines Adh f6n will be employed in the studies of alleloenzyme properties and to identify regulatory DNA sequences. Molecular biology methods will be employed to monitor the flux through alcohol degrading pathways. Metabolic inhibitors and null mutations will be used to block metabolic pathways for experimental purposes. The information gained about the regulation of ethanol metabolism and the manners in which ADH interacts with other enzymes top promote alcohol tolerance will complement the research on the Adh gene performed by molecular and population geneticists. Chronic alcoholism is a health hazard to many humans. The proposed research may provide indications of the metabolic and genetic limitations of ethanol adaptation, and thus aid this aspect of human health care.